Nitration of toluene and nitrotoluenes to form tnt

ABSTRACT

The invention provides a novel method for recovering and recycling nitrotoluenes contained in aqueous waste liquors obtained in the manufacture of TNT, particularly from systems for filtering vapors from spent sulfuric acid concentrators. In the novel method, the nitrotoluenes are efficiently and economically extracted from such liquors with toluene and the toluene containing the extracted nitrotoluenes is nitrated to produce TNT of military specification grade.

[ June 26, 1973 NITRATION OF TOLUENE AND NITROTOLUENES TO FORM TNT [76]Inventor: Milton Roth, ll Lenape Avenue,

Rockaway, NJ. 07866 [22] Filed: Mar. 28, 1972 [21] Appl. No.: 238,975

[52] US. Cl. 260/645 [51] Int. Cl C07c 79/10 [58] Field of Search260/645 [56] References Cited UNITED STATES PATENTS. 3,000,972 9/1961Bonetti 260/645 FOREIGN PATENTS OR APPLICATIONS 1,054,571 1/1967 GreatBritain 260/645 OTHER PUBLICATIONS Urbanski, Chemistry and Technology ofExplosives,

Vol. 1, MacMillan Co., New York, 1964, pp. 391-2 TP27047 PrimaryExaminer-Leland A. Sebastian Attorney-Harry M. Saragovitz, Edward J.Kelly,

A. Victor Erkkila et a1.

[57] ABSTRACT The invention provides a novel method for recovering andrecycling nitrotoluenes contained in aqueous waste liquors obtained inthe manufacture of TNT, particularly from systems for filtering vaporsfrom spent sulfuric acid concentrators. In the novel method, thenitrotoluenes are efficiently and economically extracted from suchliquors with toluene and the toluene containing the extractednitrotoluenes is nitrated to produce TNT of military specificationgrade.

4 Claims, No Drawings NITRATION OF TOLUENE AND NITROTOLUENES TO FORM TNTThe invention described herein may be manufactured, used and licensed byor for the Government for governmental purposes without the payment tome of any royalty thereon.

BACKGROUND OF THE INVENTION In the manufacture of the high explosive2,4,6- trinitrotoluene, usually referred to simply as TNT, large amountsof aqueous waste liquors containing isomeric diand trinitrotoluenes areproduced and are generally discharged into streams. These aqueousliquors turn red by photochemical reaction and give rise to a severepollution problem. No economically satisfactory method has been devisedfor treating such liquor to eliminate this pollution problem.

SUMMARY OF THE INVENTION Accordingly, it is an object of this inventionto provide a process for economically treating aqueous waste I liquorscontaining mono-, diand trinitrotoluenes to recover their content ofnitrotoluenes and thereby eliminate the pollution problem associatedwith such liquors.

Another object is to provide a simple and economical process forrecovering and recycling mono-, diand trinitrotoluenes present inaqueous waste liquors, as produced in the manufacture of TNT.

The foregoing objects can be achieved according to the present inventionby extracting aqueous waste liquors containing mono-, diandtrinitrotoluenes with toluene and then recycling the toluene extractthus obtained to the nitration reaction. In particular, the process ofthe invention comprises subjecting waste liquors containing smallamounts, e.g., less than about 0.1 percent by weight, of diandtrinitrotoluenes, as obtained in systems for filtering vapors from spentacid concentrators in TNT plants, to extraction with toluene, andnitrating the toluene containing such extracted nitrotoluenes inconventional manner with a mixture of nitric and sulfuric acids toproduce TNT of military specification grade.

I have discovered not only that toluene is an efficient solvent which iscapable of completely removing monodiand trinitrotoluenes from diluteaqueous waste liquors containing same, but that the toluene solutionthus obtained containing significant amounts, e.g. between about 0.lpercent and percent by weight, of such nitrotoluenes, particularlymixtures of isomeric diand trinitrotoluenes, can be nitrated, under thesame conditions as used for nitrating purified toluene to TNT, toproduce military specification grade TNT in excellent yield. This wasnot to be expected, since in the past it has been considered necessaryto employ a toluene starting material of good purity for manufacturingmilitary specification grade TNT.

In carrying out the process of the present invention, a relatively smallamount of toluene is sufficient to completely remove the mono-, diandtrinitrotoluenes from aqueous waste liquors. For example, as little as 1volume of toluene can be used to completely extract and remove thenitrotoluenes at room temperature from about 150 volumes of aqueouswaste liquor, which contains about 0.03 percent by weight of saidnitrotoluenes, consisting of a mixture of isomeric diandtrinitrotoluenes, together with small amounts of sulfuric and nitricacids. This can be accomplished in a plurality of extraction steps, forexample, by vigorously agitating 1 volume of toluene with 2 volumes ofthe aqueous waste liquor, then allowing the toluene and aque- 5 ousphases to separate and reusing the toluene phase to extract additionalwaste liquor in similar manner. The extraction can be carried outdiscontinuously or continuously, for example, by flowing streams oftoluene and the aqueous waste liquor in 1:2 or other suitable ratio,counter-currently or cocurrently through a vertical column provided withsuccessive agitation and settling zones, and recycling the toluene phaseas long as it is capable of completely removing the nitrotoluenes fromthe aqueous phase before the latter leaves the column. The toluenerecycled in this manner gradually increases in concentration ofdissolved mono-, diand trinitrotoluenes and ultimately is no longer ableto completely remove such nitrotoluenes from the aqueous waste liquor,so that when that point is reached the recycled toluene is replaced byfresh toluene. During the extraction process of the present inventionavery small amount of toluene is transferred to the aqueous waste liquordue to its negligible, albeit finite, solubility in water. If necessaryor desired, the toluene can be removed from such liquors in suitablemanner, e.g. by absorption with activated carbon columns from which thetoluene can be recovered by heating in known manner.

EXAMPLE 1 The aqueous waste liquor subjected to extraction with toluenewas obtained from a Mahon fog filter used to scrub vapors produced froma spent sulfuric acid concentrator in a TNT manufacturing plant. It isreferred to as Mahon water in the following examples and had thefollowing chemical anaysis:

Characteristics of Mahon Water Color Very light straw Solids in waterPart A. Extraction of Mahon Water With Toluene 1,000 ml of the Mahonwater was vigorously agitated for several minutes with 500 ml of reagentgrade toluene at room temperature, after which the layers were allowedto separate and the aqueous layer was discarded. The toluene layer thusobtained was agitated with another 1,000 ml portion of the Mahon waterin similar manner and the aqueous layer was discarded. The procedure wasrepeated until a total of 76 1,000 ml portions of the Mahon water hadbeen extracted. The total content of nitrotoluenes in the final toluenelayer thus obtained was determined by analysis to be 6.4 percent byweight. The first through the final aqueous layers obtained above wereexamined for absorbance in the ultraviolet region between 225 mu and 300mu; they showed no abs'orbance band with a maximum at 275 mucorresponding to the presence of nitrotoluenes, indicating that thetoluene had completely extracted the nitrotoluenes from the Mahon water.Part B. Nitration of Toluene Extract to TNT Note: The nitration methodemployed below on a laboratory scale is identical to the standardprocedure used for nitrating toluene in the commercial manufacture ofmilitary grade TNT.

Mononitration 1,375 g of mixed acid (H SO HNO of the composition givenbelow (1) was placed in a 250 ml threeneck, round bottom flask equippedwith a stirrer, thermometer, air condenser and addition funnel. Vigorousstirring was started and the temperature was increased to 4043C with awater bath. 214 g of the toluene extract containing 6.4 percentnitrotoluenes obtained in part A was then added. The temperature wasallowed to rise slowly to 57C at a rate of approximately 2.5C/min at thebeginning of the toluene addition, and then maintained during theremainder of its duration, which took a total of 13 minutes. The darkred reaction mixture then was held at that temperature for 4 minutes,and subsequently allowed to cool to 53C with reduced stirring. Thestirrer then was stopped. When the temperature reached 51C the mixturewas poured into a separatory funnel. At 46C the acid was drained and themono-oil (MNT) was collected. The product weighed 346 g.

Binitration 1,172 g of mixed acid of the composition noted below (2) wasplaced in a 300 ml round bottom threeneck flask equipped with athermometer, air condenser, stirrer, addition funnel, and heatingmantle, and also a 6 mm stopcock on the bottom in order that acid-DNTseparation could be accomplished. While stirring, the temperature wasraised to 7477C. 275 g of MNT, the above mono-oil, then was addedslowly. The temperature was not allowed to exceed 77C for the firstminutes, but subsequently the exotherm was allowed to raise thetemperature in minutes to 85C. The remainder of the mono-oil then wasadded at that temperature over 18 minutes. After the addition wascomplete, the temperature was held at 85C for 7 minutes and then allowedto drop to 79C. After settling for 10 minutes the acid and oil wereseparated. The impure bi-oil (DNT) weighed 473 grams.

Trinitration 1,150 g of mixed acid of the composition noted below (3)was placed in a 300 ml three-neck round bottom flask fitted with astirrer, thermometer, heated addition funnel, and heating mantle. Thetemperature was raised to 91C. While stirring and maintaining thattemperature, 473 g of the bi-oil obtained above was added over 30minutes. The bi-oil was kept in the liquid state by means of the heatedaddition funnel. After all of the bi-oil was in, the temperature washeld another two minutes in order to determine whether any strongexotherm was present. This was, however, not the case. The temperaturethen was raised over 14 minutes to l 12C and held there for 4 minutes.The mixture then was cooled to 107C with stirring and then allowed tosettle and cool to 9l93C. The acid layer then was separated.

The tri-oil then was introduced into 2,500 ml of water at a temperatureof 78C. The mixture was stirred rapidly and the temperature allowed todrop to 68C. Crystallization occurred at 70C, but no evidence of atemperature rise was observed. The mixture then was maintained at 69 to71C and neutralized to pH 7.0 with 80.0 cc of 23.5% Na CO The color ofthe aqueous phase became purple during neutralization. While maintainingthe temperature, 150 cc of sellite solution (16% Na SO 1% NaHSO 83% H O)was added over 12 minutes. The color became red. The mixture then wascooled to 69C and the TNT was separated by filtration. The TNT then waswashed with water at 6567C (6 X 1,000 ml). The light yellow product wasdried under vacuum over P 0, for 2 hours. The crude TNT weighed 286 g,melting point 79.5-80.2C.

Melt Wash of Crude TNT 125 g of the crude TNT obtained above was addedto 750 ml of water at C in a 2,000 ml three-neck flask fitted withheating mantle, stirrer, thermometer, and lower drain. The temperaturewas raised to C with stirring and the water layer then was siphoned off.The molten TNT then was heated to 98C over 15 minutes with stirring. Avacuum hose was inserted into the flask to remove the water vaporproduced. When the TNT ceased to bubble and became clear it was drainedinto an aluminum sheet and cooled. The crystalline yellow TNT was brokenup and bottled. The product weighed 103 g (overall yield 62 percent),melting point 803C.

The TNT thus obtained from toluene containing 6.4 percent nitrotolueneswas of military specification grade, as shown by the following analysis:

The nitrating acids employed in the example had the followingcompositions:

Total acidity calcula- Total Total Actual Actual Nitrosyl ted assulfuric nitric sulfuric nltrlc suliurlc I sulfuric. acid, acid, acid,acid, acid, percent acld percent percent percent percent percent Thefollowing tables compare the results obtained by nitrating the aforesaidtoluene extract containing 6.4 percent nitrotoluenes and those obtainedby nitrating reagent grade toluene under the same conditions asdescribed in the foregoing example.

TABLE 1 Preparation of lvlononitrotoluenes Quantity Quantity Ratio oftoluene, mono acid, toluene to g. g. acid Toluene source A Reagent B"...Reagent plus B NT equals nitrotoluenes from Mahon water.

Product Percent yield Nitrotoluene composition, percent MNT DNT 4. Trace8. 6 1

40. 6 1.0 Trace 32. 5 1. 6 .l

TAB LE '2 Preparation of Dinitrotoluenes Quantity Quantity mono-oil,bi-acid,

Ratio oil:acid

Run No. Origin of mono-oil A Run A (Table l) B Run B (Table 1)Nitrotoluene composition, percent DNT TN T Bl-oil product, Percent yielde Overall yield of crude bi-oil calculated on the basis of initialquantity of toluene.

TABLE 3 Preparation of 'lrinitrotolucnc Quantity Quantity of bi-oil, oitri-acid,

Run No. Origin of bi-oil g. g.

A Run A (Table 2) 440 1,030 B Bun B (Table 2) 473 1,150

e Overall yield calculated on the basis of initial quantity of tolueneused.

TNT after melt-wash and drying, g.

TNT crude,

Overall yield, percent TABLE 4 Isomeric Composition TN T before selliteTNT after sellite, prior to IIIBllI'WBSll of TNT Samples Purified TNTDNT TNT Unknown DNT TNT Unknown DNT TNT Unknown Run No. 2, 4 2,3, 4

EXAMPLE 2 4,000 ml of Mahon water identical with that used in Example 1was extracted with 462 ml of toluene in 8 extraction steps as follows:500 ml of Mahon water and 462 ml of toluene were vigorously shaken in aseparatory funnel, after which the phases were allowed to separate andthe aqueous layer was discarded. The toluene layer was employed toextract the nitrotoluenes from seven 500 ml portions of the Mahon water,resulting in an extraction ratio of 1 volume toluene to 8.6 volumesMahon water. The toluene extract thus obtained, containing 0.27 percentnitrotoluenes, was nitrated and processed to purified TNT according tothe procedure described in Example 1. The TNT thus obtained was ofmilitary specification grade.

The process of the invention can be similarly utilized for treatingother aqueous liquors containing mono-, diand trinitrotoluenes, such asare obtained in the production of TNT, including manufacturing, loadingand reclaiming operations. It is unsatisfactory for use with so-calledred-water, obtained in the purification of crude TNT with sellitesolution (aqueous Na SO since most of the nitrotoluene compounds arepresent therein as water-soluble sulfonates, which in the form of thesodium salts or free sulfonic acids are not significantly soluble intoluene and hence are not satisfactorily extracted thereby.

I wish it to be understood that I do not desire to be limited to theexact method and detail of construction described for obviousmodification will occur to persons skilled in the art.

I claim:

1. A process for recovering and recycling nitrotoluenes present inaqueous waste liquor obtained in the production of TNT, which comprisesintimately mixing such liquor with toluene to dissolve and extract saidnitrotoluenes in the toluene, and subjecting the toluene solution ofsaid nitrotoluenes to nitration to form TNT.

2. A process according to claim 1, wherein said waste liquor containsdiand trinitrotoluenes.

4. A process according to claim 3, wherein the aqueous waste liquor isobtained by water washing the vapors produced in the concentration ofspent sulfuric acid recovered from the nitration of toluene to TNT witha mixture of nitric and sulfuric acids.

2. A process according to claim 1, wherein said waste liquor containsdi- and trinitrotoluenes.
 3. A process according to claim 2, wherein theaqueous waste liquor contains less than about 0.1 percent di- andtrinitrotoluenes and the amount of di- and trinitrotoluenes dissolved inthe toluene does not exceed about 10 percent.
 4. A process according toclaim 3, wherein the aqueous waste liquor is obtained by water washingthe vapors produced in the concentration of spent sulfuric acidrecovered from the nitration of toluene to TNT with a mixture of nitricand sulfuric acids.